Pulse-Field Gel Electrophoresis (PFGE)

PFGE allows investigators to separate much larger pieces
of DNA than conventional agarose gel electrophoresis. In conventional
gels, the current is applied in a single direction (from top to
bottom). But in PFGE, the direction of the current is altered at
a regular interval as shown in the animated gif below.

The gray box is the gel, the six sets of 4 black lines represent
the 3 pairs of electrodes. Initially, the gel is empty but soon Whole chromosomes
mixed with blue loading dye will be placed into the wells. Then the current
will be turned on and the direction of the current will change in a regular
pattern. This is repeated until the loading dye reaches near the end of
the gel Then the gel is soaked in a solution containing ethidium bromide
which fluoresces orange when bound to DNA.

Figure 1. Animated Gif of PFGE which will repeat one
time.
The red-striped arrows represent the direction of the current.

Figure 2. Example of a real PFGE; drug resistant Staphylococcus
aureus.
The molecular weight markers are digested lambda phage (λ)
and are given in kb.